Test Structure and e-Beam Inspection Methodology for In-line Detection of (Non-visual) Missing Spacer Defects

A test structure specifically designed to allow in-line detection of missing spacer is introduced. Missing spacer is too small to be physically detected with any current inspection tool and therefore its existence must be flagged using voltage contrast for detection with an e-beam inspection system. How this structure and methodology were used to address this defect during the ramp of a recent technology is described. Key benefits include dramatically faster learning cycles and a much better ratio of signal to noise for split experiment evaluation. Missing spacer is one example of a growing class of non- visual defects which will greatly impact future semiconductor technologies. General principles for designing test structures to detect these defect types are discussed.